1. Field of the Invention
The present invention generally relates to audio signal processing.
2. Background of the Invention
The design of high volume output audio transducers (e.g. loudspeakers) for small electronic devices is complicated. Small size restrictions in a mobile station, for example, typically limit the acoustic design to using only a very small output audio transducer. Nonetheless, high output audio levels are required to use the mobile station in speakerphone mode, which necessitates driving the output audio transducer with relatively high power. In this situation, it is not uncommon to have mechanical components within mobile station housing resonate due to vibration of the output audio transducer, which distorts the net sound being emanated by the mobile station.
In an attempt to minimize the effect of resonances, a designer of an electronic device may implement conventional equalization techniques to equalize audio output signals in order to reduce output audio volume at frequencies at which device components are known to resonate. However, the resonant frequencies of these components can vary from one device to another due to variations in manufacturing tolerances. Moreover, the resonant frequencies tend to shift over time due to components of the device loosening, grommets decaying, and general aging of the device. Thus, the use of conventional equalization techniques fails to insure long term acceptable sound quality from a small electronic device.